The present invention generally relates to hinges used for reconfiguring deployable structures, and in particular to tape-spring type deployable hinges used in such structures.
Spacecraft frequently have structural systems that are mass efficient and can be folded into a packaged state. Following launch they are subsequently unfolded or deployed to support solar arrays, antennas, instrumentation, etc. These deployable structural systems require compliance to reconfigure between packaged and deployed states and are typically implemented by one of two approaches. Most commonly, deployment is accommodated through rolling or sliding contact joint mechanisms. These articulated structures employ mechanical components such as pin-clevis joints and ball and socket joints. The second approach is to use material deformations to accommodate folding which avoids introducing imprecision arising from mechanical connections and allows the exploitation of stored strain energy to motivate self-deployment.
Recently, there has been renewed interest in the development of deployable structure architectures based on material deformations. Prior art has focused on axially prismatic or a constant cross-section along the length articulating members including shape memory alloy hinge members, tape-spring shaped hinge members, hinge members consisting of a combination of shape memory alloy and tape-spring shaped features, and non-axially prismatic folding members, such as tubes with discrete lengths slotted to form hinge regions.
Tape-spring hinges are often used in deployable structures to serve as simple and reliable hinge mechanisms with strain energy capacity, which when released, can motivate the reconfiguration of the structural system from a packaged to a deployed state. A carpenter's measurement tape is an example of a tape spring. It has geometric stiffness when extended. Tape springs used in deployable structures are typically thin shells of a elastic material, such as spring steel, copper-beryllium alloys, or carbon fiber reinforced plastic (CFRP) that are curved about their primary structural axis. They can be buckled and folded about an arc. When released they spring back to their strain free shape and have a tendency to lock into this lower energy state. Tape springs used for the members of a deployable structure can have integrated hinge regions designed for folding. Typically, if the cross-section of the tape spring is increased, the stiffness and strength performance of the member is increased. However, the more the cross-section thickness is increased, the greater the fold radius. This in turn increases the stowed volume of the structure. It is desirable to have a minimal radius of curvature of the folded hinges while maintaining the stiffness and strength of the deployed hinges. The present invention addresses this trade.